Pulmonary Dx Imaging Flashcards
Imaging w/o radiation
U/s, MRI/MRA, Bronchoscopy
initial study for respiratory sx
CXR
What structures does CXR show
lung parenchyma, pleura, chest wall, diaphragm, mediastinum, hilum
Color of CXR
gas = black fat = dark gray soft tissue = light gray bone calcification = nearly white metal = white
Indications for CXE
SOB persistent cough hemoptysis chest pain/injury fever
CXR views
PA, AP, lateral, decubitus (PA and lateral are main ones; AP only done when patient can’t get out of bed – makes structures look bigger than they actually are)
ABCDEF’s of CXR
Airway Bone Cardiac Diaphragm Edges Fields of lungs
Lateral view CXR
good for seeing lower lobes
apical lordotic view use
seeing something in apex of lung (ex. TB)
PA and lateral decubitus CXR use
determine pus vs. fluid (fluid moves b/c it is free flowing) – subpulmonic effusion
Benefits of CXR
non-invasive low radiation inexpensive convenient widely available
Pulmonary infarct
“Hampton’s hump”
triangular shape w/ base along chest wall; clot causes loss of circultation in lung leading to infarct
Risks/limitations of CXR
radiation exposure
pregnancy
can’t detect some conditions (small cancers, pulmonary emboli)
Why order a CT?
clarify abnormal CXR dx clinical sx (SOB, cough, CP, fever) characterize pulmonary nodules detect and stage primary and metastatic neoplasms lung cancer screening evaluate mediastinal or hilar masses
Lung cancer screening
55-80 yo w/ 30 pack/yr hx and currently smoke OR quit w/i past 15 years
Types of CT scans
conventional helical high resolution (HRCT) low dose CT CT angiography
conventional CT
10 mm slice
“step and shoot”; 25-30 min
Helical CT
aka spiral CT
faster
continuous
<5 min
HRCT
better detail, 1 mm slice
Low dose CT
used for screening, less detail
Multidetector/multislice CT
64 x faster, but higher radiation
Benefits of CT
fast, widely available detailed images real-time imaging for bx can be performed w/ implanted device less expensive and sensitive to movement than MRI
Risk/limitations of CT
Radiation exposure increased CA risk fetal exposure during pregnancy contrast issues body habitus >450 lbs
Special populations for CT
peds: more radiosensitive, increased risk of leukemia and brain tumors
pregos: in utero exposure linked to ped CA mortality (always ask LMP before imaging)
CT contrast
iodine
Goal of contrast
enhance differences in densities of various structures
When to use contrast?
masses, CA, metastatic, obstructive processes, PE or dissection
Non-contrast use
eval of diffuse lung disease (HRCT)
follow up of primary nodules
Risk of CT w/ contrast
allergic rxn
contrast induced nephropathy
lactic acidosis if taking glucophage (metformin) – hold 48 hrs after imaging
Allergic rxn from contrast
develops 5-60 min after
flushing, pruritus, urticaria, angioedema, bronchospasm, and wheezing, stridor, HTN, loss of consciousness
Risk factor for allergic rxn to contrast
prior rxn
asthma
atopy
How to avoid contrast rxn
pre-treat w/:
Prednisone & Diphenhydramine (Benadryl)
Contrast induced nephropathy
serum Cr >25% from baseline or >0.5 mg/dL
usually reversible
Caution using contrast in pts w/ impaired kidney function
Impaired kidney function considered
Cr >1.5 or GFR <60
When to check renal function before iodine contrast
age >60 hx of renal disease (dialysis, single kidney, kidney transplant, renal cancer, renal surgery) HTN treated w/ meds DM Glucophage (metformin)
Glucophage
eGFR >30 - med doesn’t need to be withheld
AKI or severe CKD w/ eGFR <30 - hold metformin x 48 hrs; resume after eval of renal funciton (avoiding lactic acidosis)
Pulmonary Angiography types
CTA or direct pulmonary angiography (catheter into patients)
Angiography use
assess vasculature; done w/ CT, MRI or X-ray (direct)
CTA
blood vessel detail; used for suspected PE, aortic dissection , SVC syndrome
identify vascular malformations
assess pulmonary arterial invasion by neoplasm
CTPA benefits
less invasive than direct
precise anatomical guidance if surgery warranted
safer than conventional angiography
Risks/limitations of CTPA
can miss sub-segmental PES allergy to contrast nephrotoxicity radiation body habitus >450 lbs
Gold standard for PE
direct pulmonary angiography
What is direct pulmonary angiography?
needle/catheter inserted into right femoral or internal jugular vein –> R side heart –> pulm arteries
dye injected, x-rays taken
When do you use direct pulmonary angiography
if V/Q or CTPA inconclusive but still have high clinical suspicion
Risk of direct pulmonary angiography
bleeding/hematoma at insertion site heart arrhythmia allergic rxn to contrast impaired kidney function radiation
MRI use
limited in pulm disease
hilar or mediastinal densities, sulcus tumors, cysts, lesions of chest wall
if patient has allergy to iodine or renal disease (GFR <60)
Benefits of MRI
no bone artifact as w/ CT
no radiation
Contrast for MRI
gadolinium
Limitations of MRI/MRA
pt must remain still
clautrophobia
body habitus
risk of nephrogenic systemic fibrosis (irreversible) - avoid gadolinium if GF <30 ml/min
Contraindications of MRI/MRA
pacemaker/defibrillator
metal in eye
aneurysm clip
cochlear implant
Nuclear imaging types
VQ
PET scan
VQ use
PE
pre-op assessment prior to lung resection
VQ mismatch
imbalance of blood flow and ventilation
V/Q scan phases
IV phase: tech-99m (labeled to human albumin) injected and follows blood flow (perfusion)
inhalation phase: radio-labeled xenon gas demonstrates distribution of ventilation
Benefits of V/Q
allergic rxn to radiopharm is rare
low dose radiation
Test of choice for PE in pregnant women
useful in estimating postop reserve capacity for those undergoing lung resection
TOC for PE in pregos
V/Q
Limitations of V/Q scan
sensitive for PE, but poorly specific (high false positives)
best utilized in those w/ normal CXR
no absolute contraindications
PET scan
physiologic images
radiation emitted from fluorodeoxyglucose (FDG)
FDG
radioactive glucose
accumulates in tissues/organs w/ high metabolic activity (cancer cells)
measurement of PET scan
SUV >2.5 raises probability of malignancy
Use of PET scan
detect cancer
metastasis
examine effects of cancer therapy
Benefits of PET scan
detect changes in anatomy before apparent w/ CT and MRI
radioactivity is short-lived
Limitations of PET scan
radiation
false + (inflammatory lesions, granulomas)
false - w/ slow growing tumors
time sensitive - radioactive substance decays quickly
high cost
Indications for U/S
bedside detection of pleural fluid or pneumothorax
guidance for thoracentesis
guidance for placement of thoracostomy tubes
Benefits of u/s
no radiation
portable units
u/s of normal lung
seashore sign
barcode or stratosphere sign
pneumothorax (no motion lung)
Broncoscopy indications
pneumonia, hemoptysis, cough dx tracheoesophageal fistulas and tracheobronchomalacia tissue sampling removal of excess mucus or FBs ET tube placement
Rigid bronchoscopy
used for pts w/ obstruction of trachea or a proximal bronchus; for removal of debris (FB)
Benefits of bronchoscopy
safe low complications (nasal discomfort, sore throat, mild hemoptysis; hemorrhage, pneumothorax, Hypotension, arrhythmia)
Contraindications for bronchscopy
severe refractory hypoxia
risk of bleeding (anticoagulants, coagulopathy)
risk of respiratory and CV decompensation (asthma or COPD exacerbation current or recent MI, poorly controlled CHF, life threatening arrhythmias)
